Terracotta collaboration provided by BDCEP enables the input event information and the information generated as a result of processing the input event information to be stored and referenced in the cache of an external Terracotta server. The cache of the Terracotta server can be accessed from multiple CEP servers.
You can operate BDCEP in a scaleout configuration where input events are distributed by a load balancer at the front-end of multiple CEP servers, and the cache on the same Terracotta server is referenced. To do this, use a Virtual Data Window to store the input event information and the information generated by processing the input event information in the cache of the Terracotta server, and then specify in a complex event processing rule that a Virtual Data Window is to be used to reference the stored information.
Figure 7.1 Example of referencing an event distributed to a different CEP Server by Terracotta collaboration
Note
When using a Virtual Data Window to reference the Terracotta cache, you must use a join that specifies UNIDIRECTIONAL, ON SELECT statement, or subquery. Refer to "5.4.4.3.3 Using Terracotta cache" for details.
Data in the cache of the Terracotta server is managed as entries, with each entry made up of a key and a value. Only one entry is held for the value of a property specified as a key. You must take this into account when designing rules.
The process of referencing a Virtual Data Window for updating the data (value) in an entry is not a transaction process, so while one server is being used to reference and update data, a different server can perform an update.
